The correlation of neural signals (“brainwaves”) or neurological impulses in test animals to external and other stimuli is an important part of biological study. One way to correlate animal brainwaves to external stimuli is to track a test animal's position over time, in terms of its center of mass (“centroid”). The change of position of the test animal can be the result of external stimuli. The change of position of the test animal is also manifest as changes in brainwaves. The brainwaves can be quantified through use of a device that can measure electrical signals produced by individual neurons by way of one or more electrodes implanted in the brain or other neural materials, such as the spinal column. The change of the centroid over time can also be quantified. Therefore, reactions by the test animal to external stimuli can be quantified by correlating any changes in the centroid to changes of brainwave activity.
Typically, as the animal moves, perhaps as the result of external stimuli, the animal's image can be recorded many times per second by a video camera. The brainwaves of the test animal are also recorded by a recording device, such as a multi-channel acquisition processor (MAP), wherein the recordings are also time-stamped. Generally, a MAP can be defined as a device that is capable of recording and time-stamping at least two separate data streams at the same time. The position of the test animal, as indicated by its centroid, is calculated by a tracking device. The calculated position of the centroid is also then recorded and time-stamped by the MAP. After both the brainwaves and the centroid positions have been time-stamped and recorded by the MAP, researchers can then correlate the macroscopic behavior of the animal with its concurrent neural activity.
Within the tracking device, the position of the test animal is determined by the calculation of the centroid from video frame to video frame. After each video frame is acquired by the camera, the frame is then sent to the tracking device. The tracking device performs various operations upon each video frame, such as deleting the image of the animal's tail and the image of any wires attached to the animal's skull, increasing the contrast between the test animal and the background, and so on. After these operations are performed, the centroid of the pixels corresponding to the test animal for each video frame is calculated. As discussed above, the centroid can be generally defined as the average “middle” of the animal. Typically, the centroid is plotted in an “X-Y axis”/two dimensional coordinate plane. The test animal's position can be precisely mapped to brainwave measurements. Therefore, reactions by the animal, such as muscular movements as a result of outside stimuli, can be mapped to brainwaves.
However, certain reactions of note of the test animal do not lend themselves to be readily determined by centroid calculation. There are some reactions to external stimuli that can not be readily ascertained as a function of a change of centroid. One such reaction of the test animal is the “fear” reaction. Typically, in a fear reaction, animals “freeze” having less movement than they would if they were merely at rest, sometimes not even breathing until the fear reaction abates. In a fear reaction, the brain of the test animal generates brainwaves, which can be recorded by the MAP. For a researcher, discerning the brainwaves for a fear reaction from the brainwaves from an animal not in fear but “at rest” is a difficult task. Generally, this is because a primary indicator of animal behavior, the position of the centroid from video frame to video frame, may not change.
Therefore, there is a need for a method and a system to discern whether an animal is in a fear reaction that overcomes at least some of the problems associated with conventional fear reaction discernment systems or methods.